Magnetron



NOV. 10, 1953 J, VERWEEL 2,659,030

MAGNETRON I Filed April 15, 1950 INVFJVTOR. JAN VERWEEL AGENT Patented Nov. 10, 1953 MAGNETRON I N efl fl i ass sh t J an Verweel, Eindhoven Hartford National Bank and-Trust C Hartford, Conn., as trustee Application April 13, 1950," SeriaI No.

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imsr i ri applicationNetherlands;

May13, 1949 a p 2 Claims. (01. 315-40) This invention relates to a magnetron comprising a number of anode segments which form part of a resonator system.

Magnetrons are known in which the resonator system is built up from anumber of resonant cavities which open into the slots between two neighbouring anode segments. Although the known magnetrons are capable of producing excellent results, they have a limitation in that their manufacture is difiicult and costly and thistends to make these structures unavailable for many uses.

It is an object of this invention to provide a magnetron anode of simple construction which may be manufactured at little cost.

A further object of the invention is to provide a magnetron anode structure ,which facilitates degassing of the magnetron.

A primary object of the invention is to provide a magnetron structure in which the anode comprises a plurality of anode segments forming a part of a resonator system.

In accordance with the invention in a magnetron comprising a plurality of anode segments which form part of a resonator system the resonator system is constituted by a helix of conductive material, the shape of which helix is conformed with that of the cathode. The length of each turn of the helix should not exceed onehalf the wavelength of the generated oscillations. If the length of a turn of the helix is equal to one-half the Wavelength of the generated oscillation the adjacent anode segments oscillate in phase opposition, this wavelength being the shortest wavelength which can be produced.

The magnetrons according to the invention may be constructed either with a fiat cathode opposite to which a straight helix is arranged or with a cylindrical cathode and a circular helix arranged to surround it coaxially. The high-frequency energy may be taken from the helix by connecting two wires of a lecher wire system to two points of the helix which are comparatively close to one another. These wires may also serve as stay wires and according to the spacing between the points of attachment the helix may be interrupted between them so as to avoid the establishment of a short circuit for the lecher system. The connection of the helix to the wires of the lecher system is chosen to be such that the impedance of the helix is conformed with the lecher system.

The anode may alternatively be supported by a system of two coaxial conductors, which are connected to the helix at a suitable point.

u The helix maybe made from a thin, hollow pipe of suitable metal, so that use may be made of liquid cooling, the liquid being supplied through the; lecher wires mentioned hereinbefore.

ilnstead of leadingaway the energy generated by means of lecher wires a coupling loop may be used ending in a waveguide.

In order to assist in securing a definite manner of oscillation supplementary connections may be provided between difierent points of the helix. If the turns of the helix are equal to a half-wave length of the generated oscillations, for example, the center of the side of the helix remote from the cathode may be provided with a conductor which connects together all the turns on this side of the helix, since the high-frequency voltage of these points of the turns is equal to zero with the manner of oscillation indicated.

Since the natural frequency of the magnetron varies with the dimensions of the helix, it may be readily controlled by adjustment of the temperature of the magnetron, for instance by heating the anode with an electric current.

In order that the invention may be more clearly understood and readily carried into effect, it will now be described in detail with reference to the accompanying drawing, in which:

' Fig. 1 is a sectional view of the magnetron of invention taken at right angles to the axis of the electrode system;

Fig. 2 is a sectional view of the magnetron taken on line 11-11 of Fig. l and Fig. 3 shows another embodiment of the anode of invention in which the turns of the helix are connected together on the side of the anode remote from the cathode.

Figs. 4 and 5 show different views of a magnetron according to the invention having a flat cathode.

Fig. 6 shows a completely circular anode in which the energy is led away by a coupling loop.

Referring to Fig. l the numeral [0 designates generally a magnetron having a glass base portion I and a bulb portion 2. A cylindrical cathode 4 is secured to support wires 3 fixedly positioned in the base I and which wires also function as lead-in conductors. Surrounding the cathode 4 is a circular helix 6 which constitutes the anode of the tube system. This helix 6 may consist simply of fine wire, or may be a hollow pipe through which a cooling liquid may be circulated to facilitate cooling of the structure. N and S are the magnetic pole pieces.

As shown in Fig. 2, the bulb 2 at the level of the electrode system may have a narrowed part 1 In Figs. 4 andffi. the flatcathode is indicated by 13, the straight helix l2 being the anode.

N and S are the over shaped pole pieces. In

Fig. 6 the anode 6 is a completely closed circular helix. A coupling loop 9 ends in a wave guide H.

In one experiment conductedbyway of orienta tion, a monocrystal tungsten wire was wound on A a, rectangular mandril of 5 x 3 mms. dimensions with a pitch of about 1 mm. and put aroundata diameter of 7 mms., the parts of the helix facing the cathode being directed as far as possible -par-- allel to the axis of the cathode. The cathode had a diameter of 4 mms. At the wave length of 3 cms. even several kilowatts of pulse energy could be obtained with this arrangement.

What Iclaim is:

1. A magnetron comprising a cathode, a plurality of anode segments constituting a portion of a resonating" system and comprising a helix of conductive material, the axis of said helix encircling the cathode, each turn of the helix being equidistant from the cathode and constituting one of said anode segments, a conductor connecting the midpoints of the turns of the helix on the side remot e from, the cathode and means adjacent to said helix to produce a magnetic field traversing the helix.

7 2. n magnetron as claimed in claim 1 in which the cathode is cylindrical.

JAN VERWEEL.

References pit ed inthe file of this patent UNITED S'ILATES PATENTS .1 Number Name Date 1,417,912 Hewitt May 30, 1922 1,981,989 Clavier Jan. 15, 1935 2,009,369., Hansell July 23, 1935 2,266,411 Clavier Dec. 16, 1941 2,521,556 Wilbur Sept. 5, 1950 FOREIGN PATENTS Number Country Date 426,053;- Germany Mar. 8, 1926 663,309 g L Germany Aug. 4, 1938 

